Induction-motor.



J. LEBOVICI.

INDUCTION MOTOR.

APPLICATION FILED MAY i4, 1917.

Patented Apr. 16, 1918.

a By I W ziomvirs UNITED STA ES PATENT OFFICE.

JUSTIN LEBOVICI, 0F OAKLEY, OHIO, ASSIGNOR TO THE TRIUMPH ELECTRIC COMPANY,

A CORPORATION OF OHIO.

INDUcTIommoTon Specification of Letters Patent.

Patented Apr. 16, 1918.

Application filed May 14, 1917. Serial No. 168,395.

provements in Induction-Motors, of which the following is a specification.

The principal object of my invention is to provide a new and improved secondary member for an' induction motor with features adapting it for starting safely and advantageously.

Another object of my invention is'to provide an induction motor secondary with windings adapted for reconnection after starting and with safety devices suitably All these objects and others will be. made apparent in the following specification and claims taken in connection with the accompanying drawings in which I have illustrated two specific embodiments of my invention. I

now proceed to describe these particular forms in which my invention may be made available.

Figure 1 is an axial section of circuit changing apparatus which forms part of this embodiment of my invention;

Fig. 2 is a transverse section with parts on different planes as indicated by the lines 2 in Fig. 1;

Fig. 3 is a diagramof the windings, and

Fig. 4 isa corresponding diagram showiBng an additional stage as compared with in this case the secondary member of the motor is the rotor and its shaft 12 carries the star connected windings 10 of low re sistance per unit length each connected serially at point 8 with a respective fuse 9 and a winding 7 of high resistance per unit length. The ends of the three high resistance windings 7 are electrically connected as indicated by the numeral 6. The rotor shaft 12 also carries a collar 11 with a housing 13 in which are three contact terminals 14. connected through the wall 22, but insulated therefrom by the insulating material 15. From each point 8 there is a tap conductor 16 going to the respective contact terminal 14 and theconductors for the fuses 9 are designated 17 and 18.;

Projecting from the housing 13 are three channels 19 each with a main part 20 and side wings 21 and within each chel 19 are the two spring clips 23 to receive the respective fuse 9.

Alternately arranged with the channels 19 are the extensions 24 from the circumferential housing 13 and these chambers 24 each contain a centrifugal weight 26 pivoted at 25 and connected by a link 27 at the pivotal point 28 to the annular disk 31 at the pivotal point 29. The annular disk 31 is held to the left as viewed in Fig. 1 by the spring 37 and carries three lugs 30 which afford a construction for the pivot connections 29.

Alternately arranged with the lugs 30 on the disk 31 are three bosses 36 each provided with a socket containing a helical spring 32 which acts against the ring 34: carried by the three stems 33. This ring 34: has three contact buttons 35 in registry with the contact buttons 14..

Referring to Fig. 3, the ring 34 is represented by a dotted line and it is to be understood that normally when the motor is at rest it is out of contact with the buttons 14 and accordingly each low resistance winding 10 is connected in series with a fuse 9 and a high resistance 7. When the current is applied to the stator winding and a rotating field is produced thereby, the induction in the secondary is very powerful but the current in the secondary circuit is kept within roper bounds by the high re sistance win ings 7 in series with the low resistance windings 10 when the motor starts. This relative effect in keeping down the secondary current is due to the fact that the high resistance windings being of greater resistance per unit length (compared with the low resistance windings) are of greater resistance per turn, and therefore when the high resistance windings are in series the quotient of electromotive force divided by resistance for the whole circuit is greater than for a circuit comprising the low resistance windings alone. On the attainment of a certain critical speed, the centrifugal Weights 26 fly out in opposition to the spring 37 and close the buttons 35 on the ring 34 against the buttons 14, thus establishing the short-circuiting connection indicated by the dotted line 34- in Fig. 3. Thereafter the currents flow in the windings 10 and 7 in several circuits instead of in series, and thus as the speed of the rotor increases and the induction from the stator decreases, this reconnection of the windings permits proper currents to flow in the rotor windings to maintain the desired motor torque. The fuses 9 protect the high resistance windings 7 against the danger of burn out by improper starting conditions or otherwise. As soon as a fuse burns out, the rotor is open circuited and this protects the stator windings because under these circumstances the only current that can flow through the stator windings is the magnetizing current. The system is foolproof in several respects: the fuses must be present to make the motor operate, their re moval or blowout protects the primary windings as well as the secondary windings, they are protected mechanically by the channels 19, and the centrifugal force keeps them in their sockets or clips 23. Nevertheless on stopping the motor the fuses are readily accessible for replacement.

Referring to Fig. 4, this shows additional high resistance windings 7 interposed between the windings 10 and 7. In this case the connection 34 is to be established on the attainment of a certain critical speed, and then at a higher speed the connection 34 is made, so that the transition from initial starting condition to full running condition is made in two stages.

What I claim is:

1. In an induction motor, a secondary member having a plurality of windings, certain of said windings having a much higher resistance per turn than others of said windings, those of higher resistance having an automatic overload circuit breaker associated serially therewith, and means for changing the connections of said windings after the motor has started.

2. In an induction motor, a secondary member having a winding of low resistance per turn and a winding of high resistance per turn and an automatic overload circuit breaker in series in a closed circuit, said windings being exposed to the same degree and with additive effect to the induction from the primary member of the motor, and a normally open switch to be closed for higher motor speeds to connect together points of such closed circuit alternate with said windings whereby the said windin s will each be placed in an individual circuit through said switch.

8. in an induction motor, a secondary member having a plurality of windings of which some are of high resistance per turn and some low, means connecting said windings so that high and low resistance wind ings are normally in circuit serially with one another and subject to additive induction from the primary member of the motor, automatic overload circuit breakers serially associated with respective high resistance windings, and normally open switches to be closed for higher motor speeds to reconnect said windings in individual closed circuits, all the windings on the secondary member being at all times in closed circuits.

4. In an induction motor, a secondary member having a winding of low resistance per turn and a plurality of windings of high resistance per turn all normally connected in a closed circuit serially and subject to additive induction from the primary member of the motor, automatic overload circuit breakers serially associated with respective high resistance windings, and normally open switches to be closed successively for higher motor speeds to reconnect said windings in individual closed circuits, said switches being adapted to be closed successively first to close the circuits in succession for the high resistance windings and then for the low resistance winding, all the windings all the time being in closed circuits.

5. In an induction motor, a secondary member having a closed circuit winding, means to change the connections of said winding from starting to running condition upon the attainment of a certain speed, and an automatic overload circuit breaker amociated with said winding.

6. In an induction motor a rotor secondary having a closed circuit winding, an automatic overload circuit breaker associated therewith, and centrifugal means to short circuit a portion of said winding around said circuit breaker above a certain speed.

7. In induction motor, a rotor secondary having a closed circuit winding, and fuse clips and a fuse comprised in the circuit of said winding.

8. In an induction motor, a rotor secondary having a closed circuit winding, and fuse clips and a fuse comprised in the circuit of said winding, said fuse being placed in said clips so that centrifugal force acting thereon tends to hold it in place.

JUSTIN LEBOVIGI. 

